Collybia butyracea: Rhodocollybia butyracea
Cap 2.5-6.5 cm broad, convex, becoming broadly convex to nearly plane with a low umbo; margin incurved when young, sometimes upturned at maturity; surface smooth, lubricous, reddish-brown, tawny brown to greyish-brown, darkest at the disk, lighter in age; flesh white, thin, soft, unchanging; odor, fungal; taste mild.
Gills close, adnexed to nearly free, moderately broad, white, soon pallid, edges irregular, sometimes finely scalloped.
Stipe 2.5-5.5 cm tall, 0.5-1.0 thick, tapering to an enlarged base; surface smooth when young, faintly longitudinally striate in age, concolorous with the cap but paler; cartilaginous, stuffed, hollow at maturity, often with white to pallid, cottony mycelium at the base.
Spores 6-7.5 x 3.5-4.0 microns, smooth, elliptical, inequalateral; spore print cream-buff.
Scattered to gregarious or in rings under conifers, occasionally with hardwoods; fruiting from late fall to mid-winter.
Edible, but unsubstantial. There is little local experience with this mushroom.
Rhodocollybia butyracea is characterized by a smooth, pale, reddish-brown to greyish-brown lubricous cap, nearly free gills with irregular edges, and a cartilaginous usually longitudinally striate stipe. Gymnopus dryophilus is similar but lacks the lubricous cap and has smooth gill edges.